Zac Efron's Bittersweet Birthday Wish

Zac Efron's Birthday Wish Will Break Your Heart

On October 18, Zac Efron turned the big 2-8. We celebrated this auspicious occasion by taking an investigatory look at every time one of the actor's muscles appeared to be staring straight in our direction. (And, it was glorious.)

The b-day boy had his own message to share with the world this Sunday. The We Are Your Friends star posted a throwback pic on Instagram of himself and his cousin, Emily, on the beach when they were children.

The post is bittersweet, with a poignant caption that reads: "Happy birthday to my cousin and best friend, Emily, who passed away from cancer 2 years ago," he wrote, adding, "She was 28 like me."

"We share the same birthday and this day is forever ours," he continued. "My birthday wish is for you to donate anything you can to @su2c. The link is in my bio. Thank you everyone for all the birthday wishes. Love you."

Stand Up 2 Cancer is a nonprofit dedicated to raising money for cancer research. Efron has been affiliated with the organization since 2010, when he teamed up with Vanessa Hudgens, Dakota Fanning, and other stars in the PSA below. Read more about the organization here.